Green pathways to seaweed protein: a comparative techno-economic appraisal of pH shifting, MAE, UAE, and EAE

Seaweeds are emerging as sustainable protein sources, yet large-scale extraction remains limited by high costs, low yields, and energy-intensive processing. This study presents a techno-economic and simplified environmental assessment of four green extraction routes for seaweed-protein recovery: pH shifting, microwave-assisted extraction, ultrasound-assisted extraction, and enzyme-assisted extraction, along with a hybrid pH-shifting + ultrasound configuration. Process models were developed from peer-reviewed data and current market information for Ulva biomass. Capital and operating costs, profitability indicators, energy use, and carbon emissions were evaluated under different product prices, protein recoveries, and drying options. Microwave-assisted extraction achieved the highest recovery (50%) and lowest carbon intensity (10.8 kg CO₂ per kg protein). Drying dominated both cost and energy demand, representing more than two-thirds of total investment and electricity use. Replacing freeze- with oven-drying improved financial performance but increased emissions, while higher protein recovery enhanced both economic and environmental outcomes. The hybrid pH–ultrasound route offered a balanced compromise between efficiency and simplicity. This comparative appraisal provides the first integrated assessment of economic and environmental trade-offs across green extraction pathways, offering strategic insights for scaling seaweed protein production sustainably. Microwave-assisted and hybrid pH-shifting + ultrasound methods achieve the best balance between cost, efficiency, and environmental impact for seaweed-protein extraction • Drying dominates CAPEX and energy, making it the key optimisation target. • MAE gives 50% recovery and low CO₂ but depends on drying and product price. • Hybrid pH + UAE improves recovery; oven drying cuts CAPEX but raises emissions. • UAE needs higher recovery; EAE is enzyme-cost heavy; pH shift is price-sensitive. • Literature-based TEA shows scaling needs efficient, low-energy drying systems.